US4730906A - Bright wide-angle zoom lens - Google Patents
Bright wide-angle zoom lens Download PDFInfo
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- US4730906A US4730906A US06/868,461 US86846186A US4730906A US 4730906 A US4730906 A US 4730906A US 86846186 A US86846186 A US 86846186A US 4730906 A US4730906 A US 4730906A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B15/00—Optical objectives with means for varying the magnification
- G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
- G02B15/142—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having two groups only
- G02B15/1425—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having two groups only the first group being negative
Definitions
- the present invention relates to a bright wide-angle zoom lens which may be typically incorporated in an SRL camera.
- zoom lenses of the retrofocus type which are composed, in order from the object side, of a negative lens group and a positive lens group, and this has made a contribution to the increasing use of wide-angle zoom lenses that are adapted for use with SRL cameras.
- One disadvantage of the wide-angle zoom lens is that it is not as bright as the fixed focus lens. Efforts have been made to design a bright zoom lens that is solely composed of the design elements used in the conventional lens system consisting of spherical lens elements but these efforts have met with limited success in commercial terms for various reasons such as insufficiency of optical performance and an undesirably large optical system.
- the primary object of the present invention is to provide a compact and very bright zoom lens of high performance by making use of the increased degree of freedom afforded by the new concept of a lens element having a refractive index gradient profile along the optical axis, this concept having seen remarkable advances in the art and having been utilized in many fields on an increasingly commercialized scale.
- the present invention provides a compact and high-performance bright wide-angle zoom lens comprising, in order from the object side, a front group having a negative refractive power and a rear group having a positive refractive power, with a stop diaphragm being disposed between the front and rear groups, said front group, said stop diaphragm and said rear group being capable of independent mechanical movement in response to a change in the focal length of the overall system.
- said rear group having a positive refractive power is composed, in order from the object side, of a positive lens unit, a negative lens unit, and a positive lens unit, with a lens element having a refractive index gradient profile along the optical axis being disposed in the positive lens unit on the image side of the rear group.
- the lens element having a refractive index gradient profile along the optical axis satisfies the following relationship:
- ⁇ N is the absolute value of the change in the refractive index of said lens element.
- the front group having a negative refractive power is composed, in order from the object side, of a positive lens, negative lens, negative lens, positive lens, negative lens, and a positive lens; and the rear group having a positive refractive power is composed of a positive lens unit, a negative lens unit, and a positive lens unit, said first positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of positive and negative lenses, a positive lens, and a positive lens having a surface with a smaller radius of curvature directed toward the object side, said negative lens unit being composed of a negative lens having a surface with a smaller radius of curvature directed toward the image side, said second positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of negative and positive lenses and a positive lens, and the positive lens which is closest to the image side being a lens element having a refractive index gradient profile along the optical axis.
- FIG. 1 is a cross-sectional view of the zoom lens system constructed in Example 1 for the wide-angle position;
- FIGS. 2, 3 and 4 are graphs plotting the aberration curves obtained in Example 1 at the wide-angle, middle-angle and narrow-angle positions, respectively;
- FIG. 5 is a cross-sectional view of the zoom lens system constructed in Example 2 for the wide-angle position.
- FIGS. 6, 7 and 8 are graphs plotting the aberration curves obtained in Example 2 at the wide-angle, middle-angle and narrow-angle positions, respectively.
- the present invention provides a wide-angle zoom lens and its overall system is of the retrofocus type composed, in order from the object side, of a negative front group and a positive rear group.
- the first lens group for focusing in the wide-angle zoom lens may be a positive lens group, but more desirably, focusing is accomplished by a negative lens group because this reduces the aberrational variations resulting from changes in the object distance and is effective for the purpose of producing a bright lens system.
- a positive group as the first lens group of a long backfocus zoom lens system adapted for use with an SLR camera, a complex arrangement involving three or more movable lens groups is necessary.
- the stop diaphragm is designed to be movable as a unit together with the rear group, the occurrence of coma flare at narrow angle position is unavoidable, and a bright zoom lens of the type contemplated by the present invention will experience the fatal problem of reduced contrast in the low-frequency range.
- this problem is eliminated by disposing the stop diaphragm between the front and rear groups and by allowing the front group, the stop diaphragm and the rear group to be moved mechanically and independently of each other in response to a change in the focal length of the overall system.
- a lens element in the positive lens group close to the image side and provided with a refractive index gradient profile which is a function solely depending upon co-ordinates i.e., so-called axial gradient index
- axial gradient index is effective in correcting the spherical and coma aberrations that may occur in a bright or high-speed lens which inherently involves considerable difficulty in correcting these aberrations.
- An additional advantage of economy results from the fact that the lens in the rear group which is close to the image side has a small diameter among the lens elements used in the system because it is costly to produce a large-diameter lens having a refractive index index gradient profile.
- the front group composed of positive, negative, negative, positive, negative and positive lenses in order from the object side will provide greater effectiveness in correcting distortions and spherical aberrations by means of combining this front group with the rear group.
- ⁇ N is preferably within the range of from 0.02 to 0.06.
- f is the focal length
- F NO is the f-number
- ⁇ is the half view angle
- r is the radius of curvature of a specific lens surface
- d is the thickness of a specific lens or the aerial distance between adjacent lenses
- Na, Nb and Nc represent the refractive indices of a specific lens at wavelengths of 0.5682 ⁇ m, 0.6471 ⁇ m and 0.488 ⁇ m, respectively.
- the lens closest to the image side has a refractive index profile, and a specific value of its refractive index N is given by: ##EQU1## where x represents the distance of a certain point from the reference surface which is the plane on the object side of the final lens element having a refractive index profile, with the positive value of x being taken in the direction approaching the image side.
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- Optics & Photonics (AREA)
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Abstract
A compact and high-performance bright wide-angle zoom lens comprising, in order from the object side, a front group having a negative refractive power and a rear group having a positive refractive power, with a stop diaphragm being disposed between the front and rear groups. The front group, stop diaphragm and rear groups are capable of independent mechanical movement in response to a change in the focal length of the overall system. The rear group having a positive refractive power is composed, in order from the object side, of a positive lens unit, a negative lens unit, and a positive lens unit, with a lens element having a refractive index gradient profile along the optical axis being disposed in the positive lens unit on the image side of the rear group.
Description
The present invention relates to a bright wide-angle zoom lens which may be typically incorporated in an SRL camera.
Recent advances in the technology of zoom lenses have been remarkable. Particularly great advances have been made in zoom lenses of the retrofocus type which are composed, in order from the object side, of a negative lens group and a positive lens group, and this has made a contribution to the increasing use of wide-angle zoom lenses that are adapted for use with SRL cameras. One disadvantage of the wide-angle zoom lens is that it is not as bright as the fixed focus lens. Efforts have been made to design a bright zoom lens that is solely composed of the design elements used in the conventional lens system consisting of spherical lens elements but these efforts have met with limited success in commercial terms for various reasons such as insufficiency of optical performance and an undesirably large optical system. An alternative approach toward a bright zoom lens that features a higher performance and which is more compact in size depends on employing several aspherical surfaces within the optical system, but even with the state-of-the-art lens technology available today, lenses with aspherical surfaces are difficult to produce and involve high processing costs.
The primary object of the present invention is to provide a compact and very bright zoom lens of high performance by making use of the increased degree of freedom afforded by the new concept of a lens element having a refractive index gradient profile along the optical axis, this concept having seen remarkable advances in the art and having been utilized in many fields on an increasingly commercialized scale.
In order to attain the aforementioned object, the present invention provides a compact and high-performance bright wide-angle zoom lens comprising, in order from the object side, a front group having a negative refractive power and a rear group having a positive refractive power, with a stop diaphragm being disposed between the front and rear groups, said front group, said stop diaphragm and said rear group being capable of independent mechanical movement in response to a change in the focal length of the overall system. In accordance with the present invention, said rear group having a positive refractive power is composed, in order from the object side, of a positive lens unit, a negative lens unit, and a positive lens unit, with a lens element having a refractive index gradient profile along the optical axis being disposed in the positive lens unit on the image side of the rear group.
In a preferred embodiment of the zoom lens having the features described above, the lens element having a refractive index gradient profile along the optical axis satisfies the following relationship:
0.02<ΔN<0.06
where ΔN is the absolute value of the change in the refractive index of said lens element.
To state the lens arrangement of this zoom lens more specifically, the front group having a negative refractive power is composed, in order from the object side, of a positive lens, negative lens, negative lens, positive lens, negative lens, and a positive lens; and the rear group having a positive refractive power is composed of a positive lens unit, a negative lens unit, and a positive lens unit, said first positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of positive and negative lenses, a positive lens, and a positive lens having a surface with a smaller radius of curvature directed toward the object side, said negative lens unit being composed of a negative lens having a surface with a smaller radius of curvature directed toward the image side, said second positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of negative and positive lenses and a positive lens, and the positive lens which is closest to the image side being a lens element having a refractive index gradient profile along the optical axis.
FIG. 1 is a cross-sectional view of the zoom lens system constructed in Example 1 for the wide-angle position;
FIGS. 2, 3 and 4 are graphs plotting the aberration curves obtained in Example 1 at the wide-angle, middle-angle and narrow-angle positions, respectively;
FIG. 5 is a cross-sectional view of the zoom lens system constructed in Example 2 for the wide-angle position; and
FIGS. 6, 7 and 8 are graphs plotting the aberration curves obtained in Example 2 at the wide-angle, middle-angle and narrow-angle positions, respectively.
The present invention provides a wide-angle zoom lens and its overall system is of the retrofocus type composed, in order from the object side, of a negative front group and a positive rear group. The first lens group for focusing in the wide-angle zoom lens may be a positive lens group, but more desirably, focusing is accomplished by a negative lens group because this reduces the aberrational variations resulting from changes in the object distance and is effective for the purpose of producing a bright lens system. In this connection, it should be mentioned that in order to use a positive group as the first lens group of a long backfocus zoom lens system adapted for use with an SLR camera, a complex arrangement involving three or more movable lens groups is necessary.
If, in the conventional zoom lens of the two-group type, the stop diaphragm is designed to be movable as a unit together with the rear group, the occurrence of coma flare at narrow angle position is unavoidable, and a bright zoom lens of the type contemplated by the present invention will experience the fatal problem of reduced contrast in the low-frequency range. In accordance with the present invention, this problem is eliminated by disposing the stop diaphragm between the front and rear groups and by allowing the front group, the stop diaphragm and the rear group to be moved mechanically and independently of each other in response to a change in the focal length of the overall system.
In accordance with the present invention, a lens element in the positive lens group close to the image side and provided with a refractive index gradient profile which is a function solely depending upon co-ordinates (i.e., so-called axial gradient index) is effective in correcting the spherical and coma aberrations that may occur in a bright or high-speed lens which inherently involves considerable difficulty in correcting these aberrations. An additional advantage of economy results from the fact that the lens in the rear group which is close to the image side has a small diameter among the lens elements used in the system because it is costly to produce a large-diameter lens having a refractive index index gradient profile.
In addition, the front group composed of positive, negative, negative, positive, negative and positive lenses in order from the object side will provide greater effectiveness in correcting distortions and spherical aberrations by means of combining this front group with the rear group.
If the value of ΔN is smaller than 0.02, the intended correction of aberrations is not realized. If, on the other hand, ΔN is greater than 0.06, difficulty is encountered with fabricating a lens having the desired refractive index profile. Therefore, ΔN is preferably within the range of from 0.02 to 0.06.
Two specific examples of the present invention are hereunder described, wherein f is the focal length, FNO is the f-number, ω is the half view angle, r is the radius of curvature of a specific lens surface, d is the thickness of a specific lens or the aerial distance between adjacent lenses, and Na, Nb and Nc represent the refractive indices of a specific lens at wavelengths of 0.5682 μm, 0.6471 μm and 0.488 μm, respectively.
______________________________________
f = 28.8˜35.0˜48.0 F.sub.NO = 1:2.25˜2.55˜2.90
ω = 38.3°˜32.3°˜24.2°
______________________________________
Surface
No. r d Na Nb Nc
______________________________________
1 151.755 3.11 1.73654
1.73106
1.74504
2 921.764 0.20
3 106.300 1.20 1.83633
1.82814
1.84942
4 25.970 3.31
5 38.754 1.50 1.83633
1.82814
1.84942
6 27.450 5.54
7 317.405 2.58 1.72539
1.71847
1.73655
8 -200.000 1.80
9 -87.610 1.20 1.63975
1.63646
1.64638
10 71.800 0.20
11 39.010 4.24 1.80843
1.79712
1.82717
12 232.266 Variable
13 -254.587 3.57 1.83685
1.82965
1.84818
14 -33.124 1.15 1.85029
1.83768
1.87133
15 -70.680 0.20
16 110.000 2.46 1.80580
1.79941
1.81578
17 -525.000 0.20
18 22.910 4.60 1.83633
1.82814
1.84942
19 61.411 3.34
20 719.556 5.00 1.85029
1.83768
1.87133
21 21.273 2.42
22 83.484 1.00 1.83685
1.82965
1.84818
23 21.776 6.49 1.56968
1.56629
1.57482
24 -105.520 0.20
25 ∞ 3.00 varies as shown below
26 -34.055
______________________________________
28.8 35.0 48.0
______________________________________
18.36 12.41 2.93
d.sub.12
stop stop stop
diaphragm diaphragm diaphragm
11.64 6.22 1.39
______________________________________
ΔN = 0.0309
______________________________________
______________________________________
f = 28.8˜35.0˜48.0 F.sub.NO = 1:2.25˜2.55˜2.90
ω = 38.3°˜32.3°˜24.3°
______________________________________
Surface
No. r d Na Nb Nc
______________________________________
1 227.465 3.06 1.51718
1.51414
1.52177
2 -919.110 0.20
3 98.688 1.20 1.83633
1.82814
1.84942
4 25.119 3.93
5 43.799 1.50 1.73088
1.72170
1.74598
6 30.483 5.09
7 1081.085 2.18 1.74351
1.73396
1.75925
8 -230.069 1.98
9 -82.020 1.20 1.62149
1.61764
1.62740
10 80.646 0.20
11 42.367 4.28 1.80843
1.79712
1.82717
12 927.908 Variable
13 -368.365 3.74 1.78775
1.78120
1.79807
14 -33.324 1.15 1.85029
1.83768
1.87133
15 -67.654 0.20
16 93.816 2.50 1.80580
1.79941
1.81578
17 -1903.529 0.20
18 23.039 5.24 1.83633
1.82814
1.84942
19 55.039 2.99
20 319.618 5.00 1.85029
1.83768
1.87133
21 20.934 3.05
22 76.266 1.00 1.83685
1.82965
1.84818
23 21.619 6.04 1.56968
1.56629
1.57482
24 -111.609 0.20
25 ∞ 3.00 varies as shown below
26 -35.265
______________________________________
28.8 35.0 48.0
______________________________________
18.20 13.22 2.28
d.sub.12
stop stop stop
diaphragm diaphragm diaphragm
11.15 4.72 1.31
______________________________________
ΔN = 0.0309
______________________________________
In each of the examples shown above, the lens closest to the image side has a refractive index profile, and a specific value of its refractive index N is given by: ##EQU1## where x represents the distance of a certain point from the reference surface which is the plane on the object side of the final lens element having a refractive index profile, with the positive value of x being taken in the direction approaching the image side.
The respective values of a0, a1, a2, a3 and a4 are as follows:
λ=0.5682 μm:
a0 =1.5033+0.0364=1.5397
a1 =0.590943×10-2
a2 =-0.573897×10-2
a3 =-0.190085×10-2
a4 =-0.160811×10-3
λ=0.6471 μm:
a0 =1.5001+0.0355=1.5356
a1 =0.549239×10-2
a2 =-0.571981×10-2
a3 =-0.187696×10-2
a4 =-0.159504×10-3
λ=0.488 μm:
a0 =1.5084+0.0375=1.5459
a1 =0.601061×10-2
a2 =-0.597036×10-2
a3 =-0.197622×10-2
a4 =-0.167942×10-3
Claims (8)
1. In a compact and high-performance bright wide-angle zoom lens comprising, in order from the object side, a front group having a negative refractive power and a rear group having a positive refractive power, with a stop diaphragm being disposed between the front and rear groups, said front group, said stop diaphragm and said rear group being capable of independent mechanical movement in response to a change in the focal length of the overall system, the improvement wherein the rear group having a positive refractive power is composed, in order from the object side, of a positive lens unit, a negative lens unit, and a positive lens unit, with a lens element having a refractive index gradient profile along the optical axis being disposed in the positive lens unit on the image side of the rear group.
2. The zoom lens according to claim 1 wherein said lens element having a refractive index gradient profile along the optical axis satisfies the following relationship:
0.02<ΔN>0.06
where ΔN is the absolute value of the change in the refractive index of said lens element.
3. The zoom lens according to claim 1 wherein said front group having a negative refractive power is composed, in order from the object side, of a positive lens, negative lens, negative lens, positive lens, negative lens, and a positive lens.
4. The zoom lens according to claim 1, wherein said rear group having a positive refractive power is composed of a positive lens unit, a negative lens unit, and a positive lens unit, said first positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of positive and negative lenses, a positive lens, and a positive lens having a surface with a smaller radius of curvature directed toward the object side, said negative lens unit being composed of a negative lens having a surface with a smaller radius of curvature directed toward the image side, said second positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of negative and positive lenses and a positive lens, and the positive lens which is the closest to the image side being a lens element having a refractive index gradient profile along the optical axis.
5. The zoom lens according to claim 1, further satisfying the following chart:
______________________________________
Surface
No. r d Na Nb Nc
______________________________________
1 151.755 3.11 1.73654
1.73106
1.74504
2 921.764 0.20
3 106.300 1.20 1.83633
1.82814
1.84942
4 25.970 3.31
5 38.754 1.50 1.83633
1.82814
1.84942
6 27.450 5.54
7 317.405 2.58 1.72539
1.71847
1.73655
8 -200.000 1.80
9 -87.610 1.20 1.63975
1.63646
1.64638
10 71.800 0.20
11 39.010 4.24 1.80843
1.79712
1.82717
12 232.266 Variable
13 -254.587 3.57 1.83685
1.82965
1.84818
14 -33.124 1.15 1.85029
1.83768
1.87133
15 -70.680 0.20
16 110.000 2.46 1.80580
1.79941
1.81578
17 -525.000 0.20
18 22.910 4.60 1.83633
1.82814
1.84942
19 61.411 3.34
20 719.556 5.00 1.85029
1.83768
1.87133
21 21.273 2.42
22 83.484 1.00 1.83685
1.82965
1.84818
23 21.776 6.49 1.56968
1.56629
1.57482
24 -105.520 0.20
25 ∞ 3.00 varies as shown below
26 -34.055
______________________________________
28.8 35.0 48.0
______________________________________
18.36 12.41 2.93
d.sub.12
stop stop stop
diaphragm diaphragm diaphragm
11.64 6.22 1.39
______________________________________
ΔN = 0.0309
______________________________________
where r is the radius of curvature of a specific lens surface;
d is the thickness of a specific lens or the aerial distance between adjacent lenses; and
Na, Nb and Nc represent the refractive indices of a specific lens at wavelengths of 0.5682 μm, 0.6471 μm, and 0.488 μm, respectively.
6. The zoom according to claim 1, further satisfying the following chart:
______________________________________
f = 28.8˜35.0˜48.0 F.sub.NO = 1:2.25˜2.55˜2.90
ω = 38.3°˜32.3°˜24.3°
______________________________________
Surface
No. r d Na Nb Nc
______________________________________
1 227.465 3.06 1.51718
1.51414
1.52177
2 -919.110 0.20
3 98.688 1.20 1.83633
1.82814
1.84942
4 25.119 3.93
5 43.799 1.50 1.73088
1.72170
1.74598
6 30.483 5.09
7 1081.085 2.18 1.74351
1.73396
1.75925
8 -230.069 1.98
9 -82.020 1.20 1.62149
1.61764
1.62740
10 80.646 0.20
11 42.367 4.28 1.80843
1.79712
1.82717
12 927.908 Variable
13 -368.365 3.74 1.78775
1.78120
1.79807
14 -33.324 1.15 1.85029
1.83768
1.87133
15 -67.654 0.20
16 93.816 2.50 1.80580
1.79941
1.81578
17 -1903.529 0.20
18 23.039 5.24 1.83633
1.82814
1.84942
19 55.039 2.99
20 319.618 5.00 1.85029
1.83768
1.87133
21 20.934 3.05
22 76.266 1.00 1.83685
1.82965
1.84818
23 21.619 6.04 1.56968
1.56629
1.57482
24 -111.609 0.20
25 ∞ 3.00 varies as shown below
26 -35.265
______________________________________
28.8 35.0 48.0
______________________________________
18.20 13.22 2.28
d.sub.12
stop stop stop
diaphragm diaphragm diaphragm
11.15 4.72 1.31
______________________________________
ΔN = 0.0309
______________________________________
where r is the radius of curvature of a specific lens surface;
d is the thickness of a specific lens or the aerial distance between adjacent lenses; and
Na, Nb, and Nc represent the refractive indices of a specific lens at wavelengths of 0.5682 μm, 0.6471 μm, and 0.488 μm, respectively.
7. In a compact and high-performance bright wide-angle zoom lens comprising, in order from the object side, a front group having a negative refractive power and a rear group having a positive refractive power, with a stop diaphragm being disposed between the front and rear groups, said front group, said stop diaphragm and said rear group being capable of independent mechanical movement in response to a change in the focal length of the overall system, the improvement wherein the rear group having a positive refractive power is composed, in order from the object side, of a positive lens unit, a negative lens unit, and a positive lens unit, with a lens element having a refractive index gradient profile along the optical axis being disposed in the positive lens unit on the image side of the rear group, and wherein said front group having a negative refractive power is composed, in order from the object side, of a positive lens, negative lens, negative lens, positive lens, negative lens, and a positive lens.
8. In a compact and high-performance bright wide-angle zoom lens comprising, in order from the object side, a front group having a negative refractive power and a rear group having a positive refractive power, with a stop diaphragm being disposed between the front and rear groups, said front group, said stop diaphragm and said rear group being capable of independent mechanical movement in response to a change in the focal length of the overall system, the improvement wherein the rear group having a positive refractive power is composed, in order from the object side, of a first positive lens unit, a negative lens unit, and a second positive lens unit, said first positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of positive and negative lenses, a positive lens, and a positive lens having a surface with a smaller radius of curvature directed toward the object side, said negative lens unit being composed of a negative lens having a surface with a smaller radius of curvature directed toward the image side, said second positive lens unit being composed, in order from the object side, of a positive cemented lens comprised of negative and positive lenses and a positive lens, the last-mentioned positive lens which is the closest to the image side being a lens element having a refractive index gradient profile along the optical axis.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60-118614 | 1985-05-31 | ||
| JP60118614A JPS61275809A (en) | 1985-05-31 | 1985-05-31 | Bright wide-angle zoom lens |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US4730906A true US4730906A (en) | 1988-03-15 |
Family
ID=14740903
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US06/868,461 Expired - Lifetime US4730906A (en) | 1985-05-31 | 1986-05-30 | Bright wide-angle zoom lens |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4730906A (en) |
| JP (1) | JPS61275809A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4840467A (en) * | 1986-12-25 | 1989-06-20 | Olympus Optical Co., Ltd. | Compact zoom lens system with a high zooming ratio |
| US4842386A (en) * | 1985-06-26 | 1989-06-27 | Canon Kabushiki Kaisha | Variable focal length objective |
| US4973143A (en) * | 1988-10-31 | 1990-11-27 | Olympus Optical Co., Ltd. | Zoom lens system |
| US4998807A (en) * | 1988-08-23 | 1991-03-12 | Olympus Optical Co., Ltd. | Variable focal length lens system |
| US5002373A (en) * | 1988-02-10 | 1991-03-26 | Olympus Optical Co., Ltd. | Zoom lens system of inner focus type |
| US5011272A (en) * | 1984-12-21 | 1991-04-30 | Canon Kabushiki Kaisha | Compact zoom lens |
| GB2254933A (en) * | 1991-04-01 | 1992-10-21 | Asahi Optical Co Ltd | Two group zoom lens system with diaphragm stop |
| US5910860A (en) * | 1997-01-17 | 1999-06-08 | Asahi Kogaku Kogyo Kabushiki Kaisha | Zoom lens |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2700003B2 (en) * | 1987-01-23 | 1998-01-19 | オリンパス光学工業株式会社 | Compact wide-angle lens |
| JP3296876B2 (en) * | 1993-03-26 | 2002-07-02 | オリンパス光学工業株式会社 | Zoom lens |
| US5621574A (en) * | 1995-03-29 | 1997-04-15 | Nikon Corporation | Objective lens system utilizing axial gradient index (grin) lens elements |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3729253A (en) * | 1971-05-28 | 1973-04-24 | Western Electric Co | Optical system comprising a single element having a continuously varying index of refraction |
| US4367927A (en) * | 1977-07-23 | 1983-01-11 | Olympus Optical Co., Ltd. | Zoom lens system |
| US4571032A (en) * | 1981-01-22 | 1986-02-18 | Canon Kabushiki Kaisha | Zoom lens |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6039204B2 (en) * | 1976-11-12 | 1985-09-05 | ミノルタ株式会社 | Two-component wide-angle zoom lens system |
| JPS5860717A (en) * | 1981-10-07 | 1983-04-11 | Canon Inc | High-aperture ratio zoom lens |
| JPS59149312A (en) * | 1983-02-16 | 1984-08-27 | Asahi Optical Co Ltd | Photographic lens of high aperture ratio |
-
1985
- 1985-05-31 JP JP60118614A patent/JPS61275809A/en active Pending
-
1986
- 1986-05-30 US US06/868,461 patent/US4730906A/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3729253A (en) * | 1971-05-28 | 1973-04-24 | Western Electric Co | Optical system comprising a single element having a continuously varying index of refraction |
| US4367927A (en) * | 1977-07-23 | 1983-01-11 | Olympus Optical Co., Ltd. | Zoom lens system |
| US4571032A (en) * | 1981-01-22 | 1986-02-18 | Canon Kabushiki Kaisha | Zoom lens |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5011272A (en) * | 1984-12-21 | 1991-04-30 | Canon Kabushiki Kaisha | Compact zoom lens |
| US4842386A (en) * | 1985-06-26 | 1989-06-27 | Canon Kabushiki Kaisha | Variable focal length objective |
| US4840467A (en) * | 1986-12-25 | 1989-06-20 | Olympus Optical Co., Ltd. | Compact zoom lens system with a high zooming ratio |
| US5002373A (en) * | 1988-02-10 | 1991-03-26 | Olympus Optical Co., Ltd. | Zoom lens system of inner focus type |
| US4998807A (en) * | 1988-08-23 | 1991-03-12 | Olympus Optical Co., Ltd. | Variable focal length lens system |
| US4973143A (en) * | 1988-10-31 | 1990-11-27 | Olympus Optical Co., Ltd. | Zoom lens system |
| GB2254933A (en) * | 1991-04-01 | 1992-10-21 | Asahi Optical Co Ltd | Two group zoom lens system with diaphragm stop |
| US5331464A (en) * | 1991-04-01 | 1994-07-19 | Asahi Kogaku Kogyo Kabushiki Kaisha | Zoom lens system |
| GB2254933B (en) * | 1991-04-01 | 1994-09-07 | Asahi Optical Co Ltd | Two group zoom lens system having two light blocking elements |
| US5910860A (en) * | 1997-01-17 | 1999-06-08 | Asahi Kogaku Kogyo Kabushiki Kaisha | Zoom lens |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61275809A (en) | 1986-12-05 |
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